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Problems With Rebuilt 4l80e

benjid

By benjid
in Ask A GM Technician

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benjid New Member

benjid

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Hello gang! I’m a new member to the forum so please forgive me if my question is repetitive. Also, I apologize for the editing, it is very difficult to use the editing feature when creating a post

 

I’m having problems with 4L80E rebuilt transmission and wondered if you all might be able to give me suggestions on the cause of the problem and resolution.

 

Background: 2001 Suburban 2500, 190,000 miles, tranny rebuilt in January. Primarily used for towing a boat in FL.

 

The problem began after the burb started slipping in first/second gears and reverse. I Took it to a local shop recommended by a friend who said it needed to be rebuilt. He rebuilt the tranny, added a new torque converter and a shift kit. During his first test drive the torque converter failed causing pump failure. Both parts were replaced and he gave the vehicle to me.

 

When I took the vehicle out for a test drive it shuddered at highway speed when shifting to OD. In addition, it ran very hot (> 225 deg) while pulling my boat. I took it back to the shop; they added some type of fluid to eliminate the shuddering and also plugged a hole in the valve body for the shift kit. Apparently this hole was drilled in the wrong place.

 

Upon receiving the vehicle back I took it for a test drive, boat in tow, and noticed the shuddering had subsided somewha, but was still noticeable, although very subtle. It happens the most frequently when, at highway speed, I let off the accelerator for a brief second and then accelerate. You can hear the shudder upon acceleration. In addition, the temp while towing did decrease a little, but it is still running higher than before the rebuild.

 

Finally, this weekend I was towing the boat and noticed tow/haul feature was not working.

 

Questions: 1. What do you all think is causing the ongoing subtle shuddering? 2. What do you think is causing the higher than normal temps? 3. Is the tow/haul problem related to my transmission issues or is this just coincidental?

 

Thanks to everyone in advance.

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